What’s the Best way to: store hv battery.

Is the battery you have Li-Ion or ?

 

i would get a prolong charger

 

1. Store the packs in a cool, dry place, with temperatures not exceeding maybe 30°C, or if you leave in a hot environment, use fans or home AC system blowing across the packs or modules in a garage.

Heats are always the enemies of batteries.
2. Charge the packs maybe after every two months or so, if you got that time to grid charge them. You could discharge them before charging though.

3. If I were you, I'd at every 4-6 months, swapped the batteries from the running priuses and drive for awhile, before returning the stick one back in the Prius.

 

Cycling is better than sitting, and perfectly controlled cycles (as from a grid charger/discharger) are better than drive cycles (in use in the car)

 

Good for your score! You and your friends will be in a good position if the red triangle appears on any of your vehicles...

When the pack is fully assembled and still in the car and I know its healthy and need to pull it and store it, I hook up the Prolong charger and get a full charge and balance into it for 24 hours. Then I pull it and put it on the shelf... When it's time to use it again months later I put it back in and do another charge and balance before I use it.

But your case is different, because you don't know the pack's health and it's already been pulled apart. hopefully you have a spot where you can put it and work on it periodically, because it takes a while to know is a good pack, not too mention doing reconditioning.

First thing you'll want to do is get yourself a hobby charger that they use to charge remote control toys with... A popular one is a SkyRC iMAX B6DC V2... I've also used the htrc t240 duo... Then you want to charge up each of the 28 individual modules to full charge, but be careful not to overcharge. Then after the pack sits fully charged for a few days or a few months you want to see how much each module has self discharged and put it on a spread sheet. Then use 12v 55W regular headlight bulb to measure the voltage drop in each module over the course of 2 minutes. The bad or weakest modules will lose the most voltage...

Then if the pack is relatively healthy, the next step is to discharge each module increasingly deeper with the light bulb and then recharge three times, which will recondition the pack. First discharge down to ~5v, then to ~3v, then below 1v... You'll need a fan to keep things from getting too hot when recharging from those deeper discharges. With all old Prius batteries this will restore battery capacity down near 50% in a typical 10 year-old pack up to 96%. Learn more here:
https://www.batteryuniversity.com/learn/article/how_to_restore_nickel_based_batteries

Track all these numbers on a spreadsheet. Enclosed is a sample. If you get all this done, then that pack is going to be healthier than the one in your Gen2 and maybe even your Gen3, so swap them out and repeat...

 

yeah if it was me Id swap them into the prius every so often. Once these batteries have been used a while they dont like sitting. Plus using in the prius is better than any aftermarket charger sine its getting drained and charged so often.

Its really not that hard especially since you have a complete battery. Id imagine it only takes you 15-30 at most with a complete one.